Imaging devices, which are also known as cameras, are used for capturing images of a person, object or scene as desired. Modern imaging devices use pixels to capture images. The pixels may be provided in an array, which can also be called a sensor. The pixels divide an input image in elements, and capture values for the elements of the image. These values for the image are captured by various techniques, such as numbers of electrons per pixel after a brief exposure time. The output image is typically constructed from the captured values, whether in color or in black and white.
Imaging devices can also be used for ranging, i.e., determining the distance of the person, object or scene from the imaging device. Determining the distance is also sometimes called three-dimensional imaging. The distance may be determined by flashing specially modulated light, and detecting how long is needed for the reflections of the modulated light to return to the imaging device. This is called the time-of-flight (TOF) principle, and requires demodulation of the reflected optical signals.
Imaging often uses a shutter for the pixel. The shutter can be optical, of the type that physically prevents the incoming light from reaching the pixels. A challenge with optical shutters is that they often have a high capacitance, need a high voltage swing to open and close, and therefore consume a lot of power to operate. For example, an existing design for a shutter driver consumes a power of 4.8 W for TOF operation.
Sometimes the shutter is electrical, which means the pixels become at times electrically prevented from imaging. This consumes power, however, which in turn limits the spatial resolution of the overall sensor.